A 3GPP (3rd Generation Partnership Project) based on a WCDMA (Wideband Code
Division Multiple Access) wireless access technique is being widely deployed all over the world. An HSDPA (High Speed Downlink Packet Access), which may be defined as a first evolution of the WCDMA, provides a wireless access technique with a competitive edge in the mid-term future to the 3GPP. However, as requirements and expectations of users and service providers are continuously increasing and development of competitive wireless access techniques is proceeding, a new technical evolution in the 3GPP is requested to ensure competitiveness in the future. The requirements include a reduction in costs per bit, an increase in service availability, the flexible use of frequency bands, a simple structure and an open interface, proper power consumption of user equipments, or the like.
In general, cell selection can be classified into an initial cell selection performed at an initial stage after power of a user equipment is turned on and a cell reselection performed for handover or neighbor cell measurement.
The reason for the user equipment to perform a cell reselection is to register itself to a network to receive a service from the network. If the strength or quality of signals between the user equipment and a serving cell is degraded due to the movement of the user equipment, the user equipment reselects a different cell to maintain transmission quality of data. There may be various types of criterion to perform cell selection, and different priorities may be applied to the cell selection according to systems.
In addition, for the cell selection and cell reselection, the user equipment measures signals for the serving cell and neighbor cells non-periodically/periodically. Measurement for unnecessary cells may increase power consumption of the user equipment.